Hepatic cysts represents the most common extrarenal manifestation of autosomal dominant polycystic kidney disease (ADPKD), are associated with significant clinical morbidity, and account for up to 10% of mortality in affected patients. Despite the recent identification of genes responsible for ADPKD, little is known regarding the cellular mechanisms involved in the formation and maintenance of liver cysts; or the regulation of growth and secretion in cholangiocytes, the epithelial cells affected by hepatic ADPKD. Clinical studies support a potential role for estrogen in the progression of complicated hepatic cystic disease, and laboratory studies have implicated autocrine signaling by epidermal growth factor and purinergic agonists (e.g., ATP) as key contributors to aberrant cyst growth. However, there are no tissue culture models of ADPKD-affected cholangiocytes currently available. Recent studies by ourselves and ourselves have led to new approaches to isolation and long term culture of polarized cholangiocyte models; and to the application of biophysical and molecular techniques to address the cell-specific mechanisms that modulate biliary secretion, growth, and differentiation. The proposed studies will utilize these approaches to investigate the properties of cholangiocytes derived from the cysts of ADPKD animal models to address whether the development of liver cysts in ADPKD is associated with i) disordered growth and/or secretion across biliary- derived epithelial and ii) abnormalities of autocrine/paracrine signaling pathways. The Specific Aim focus on the development of novel rat and mouse ADPKD liver cyst epithelial cell models in order to characterize mechanisms that regulate growth, differentiation, and transport in normal versus ADPKD cholangiocytes. Emphasis will be placed on the regulatory pathways that modulate ADPKD cholangiocyte secretion and differentiation by focusing on membrane transport and the potential roles of estrogen, growth factors, and purinergic signaling. The long-term goals of this project are to generate an understanding of the mechanisms that contribute to hepatic cyst pathogenesis, and to use these findings as a basis for development of pharmacological and other approaches aiming to attenuate cyst-associated morbidity in patients with ADPKD-related hepatic cysts.